This invention relates to the field of intraluminal devices, and more particularly to cannulas for delivery of fluid to a patient""s body lumen.
Vascular anastomoses, in which two vessels are surgically joined together to form a continuous channel, are required for a variety of conditions including coronary artery disease, diseases of the great and peripheral vessels, organ transplantation, and trauma. For example, in coronary artery disease, an occlusion or stenosis in a coronary artery interferes with blood flow to the heart muscle. In order to restore adequate blood flow to the heart, a graft vessel in the form of a prosthesis or harvested artery or vein is used to reroute blood flow around the occlusion. The treatment, known as coronary artery bypass grafting (CABG), can be highly traumatic to the patient""s system.
In conventional CABG a large incision is made in the chest and the sternum is sawed in half to allow access to the heart. In addition, cardiopulmonary bypass, in which the patient""s blood is circulated outside of the body through a heart-lung machine, is used so that the heart can be stopped and the anastomosis performed. In order to minimize the trauma to the patient""s system induced by conventional CABG, less invasive techniques have been developed in which the surgery is performed through small incisions in the patient""s chest with the aid of visualizing scopes. Less invasive CABG can be performed on a beating or a non-beating heart, and may avoid the need for cardiopulmonary bypass.
During beating heart surgery, the oxygen requirement of the cardiac muscle is high and any interruption in the coronary flow of blood may result in iscehmia, heamodynamic unstability, ventricular arrythmias, stunned myocardium, or myocardial infarction. However, during coronary bypass surgery, it is necessary to interrupt the flow of blood to the myocardium which is distal (i.e., downstream) to the anastomosis site while the bypass graft is sutured to the coronary artery. As a result, the myocardium distal to the anastomosis site is deprived of oxygen until the suturing is completed and the flow across the bypass graft is established. Intracoronary shunts placed at the anastomosis site have been used to allow the native coronary flow to continue irrigating the distal myocardium during the bypass surgery. The shunt may have enlarged tips to occlude the coronary vessel on either side of the anastomosis site, to keep the site clean of blood during suturing. However, the supply of blood to the distal myocardium is poor due to the presence of the lesion in the coronary artery. An alternative method of perfusing distal to the anastomosis site is the use of an intracoronary perfusion cannula, introduced into the coronary artery at the anastomosis site to deliver oxygenated blood from the patient""s aorta or other source. However, one difficulty has been insertion of the cannula into the coronary artery, and the tendency of such cannula to back out of the coronary artery during perfusion due to the back pressure from the blood.
What has been needed is a perfusion cannula providing improved perfusion of a patient""s blood vessel distal to an anastomosis site.
The invention is directed to a perfusion cannula having a proximal section configured for attachment to a source of perfusion fluid, and a distal section configured for insertion in a blood vessel, for delivering perfusion fluid to the blood vessel. The term distal as used herein should be understood to mean downstream in relation to flow of fluid within a vessel, or farther away from the physician in relation to a device manipulated by the physician. The term proximal as used herein should be understood to mean upstream in relation to flow of fluid within a vessel, or closer to the physician in relation to a device manipulated by the physician.
In one embodiment, the cannula generally comprises a shaft having a proximal end, a distal end, a distal shaft section, and a proximal shaft section which is connected to the distal shaft section between the proximal and distal ends of the distal shaft section such that an acute angle is formed between the proximal shaft section and a proximal portion of the distal shaft section. The acute angle is measured at the location at which the proximal shaft section is connected to the distal shaft section. A lumen in the elongated shaft extends within the proximal shaft section and within at least a portion of the distal shaft section, to and in fluid communication with a port in the distal end of the distal shaft section. The lumen is configured for delivery of fluid, and may be configured for slidably receiving a guidewire therein. Thus, with the proximal end of the cannula attached to a source of perfusion fluid, such as the patient""s aorta, and the distal shaft section inserted within a native blood vessel, such as a coronary artery, through a surgical incision in a wall of the blood vessel, the acute angle causes the cannula to hook or wedge onto the wall of the blood vessel at the proximal end of the incision, so that the distal shaft section is securely anchored within the blood vessel during the perfusion. Unlike a perpendicular or nearly perpendicular angle, the acute angle of the invention sandwiches the wall of the native blood vessel between the shaft sections, with a distal length of the proximal shaft section adjacent to, or preferably in contact with, an outer surface of the native blood vessel.
In one embodiment, the cannula has at least one of a proximal occluder on a proximal portion of the distal shaft section and a distal occluder on a distal portion of the distal shaft section. The distal occluder avoids leaks of the pressurized perfusion fluid around the outer surface of the distal shaft section and into the site proximal to the distal occluder. The proximal occluder occludes the blood flow from a proximal section of the native blood vessel, and provides anchoring for the cannula to prevent or inhibit the cannula from being pushed back proximally from the blood vessel by the pressure of the perfusion flow.
In one embodiment, the distal shaft section of the cannula has a lumen only within a distal portion of the distal shaft section, so that the cannula delivers perfusion fluid to the native blood vessel out the port in the distal end of the cannula. Thus, the proximal portion of the distal shaft section is a solid walled blind tube or plug, which does not allow for flow of fluid therein. The terminology blind tube as used herein should be understood to mean a member which does not have a lumen in fluid communication with ports therein which provides a fluid delivery channel through the member. Thus, in the embodiment having one or more occluders on the distal shaft section, the cannula prevents the flow of blood within the native blood vessel at the site of the distal shaft section and retrograde flow of perfusion fluid. As a result, retrograde flow of the perfusion fluid out the proximal end of the distal shaft section, that could dislodge plaque and produce embolization of particles, is avoided. In an alternative embodiment, the distal shaft section has a lumen in the proximal portion of the distal shaft section in fluid communication with the lumen in the distal portion of the distal shaft section, so that the distal shaft section provides a shunt which channels the blood flow of the native blood vessel through the lumen in the distal shaft section, or retrograde flow of perfusion fluid out the proximal portion of the distal shaft section.
One embodiment of the invention is a perfusion cannula generally comprising a shaft having a proximal end, a distal end, a proximal shaft section having a lumen, and a distal shaft section having a proximal portion with a solid proximal end, and a distal portion with a lumen in fluid communication with the proximal shaft section lumen and with a port in the distal end of the distal shaft section. In an embodiment having one or more occluders on the distal shaft section, the cannula prevents the flow of blood within the native blood vessel at the site of the distal shaft section and retrograde flow of perfusion fluid.
In a method of performing a medical procedure, the perfusion cannula of the invention is used to deliver perfusion fluid to a native blood vessel. In a presently preferred method, the distal shaft section of the perfusion cannula is inserted distal to a lesion in the blood vessel for perfusion of the blood vessel distal to an anastomosis site during bypass surgery.
The cannula of the invention, provides easy introduction of the cannula within the patient""s blood vessel. Additionally, the cannula provides for secure anchoring of the cannula within a blood vessel during perfusion, due at least in part to the acute angle between the proximal shaft section and the proximal portion of the distal shaft section. Moreover, in the embodiment having a distal shaft section with a solid proximal portion, the cannula of the invention avoids dislodging plaque in the native blood vessel from retrograde flow within or around the cannula distal shaft section. These and other advantages of the invention will become apparent from the following detailed description of the invention and accompanying exemplary figures.